Mesoporous ZSM-22 zeolite obtained by desilication: peculiarities associated with crystal morphology and aluminium distribution

Verboekend, Danny; Chabaneix, André M.; Thomas, Karine; Gilson, Jean‐Pierre; Pérez‐Ramírez, Javier

doi:10.1039/c0ce00966k

Cited by 144 publications

(165 citation statements)

References 46 publications

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“…Analysis of the Si and Al content of H-USY (40) and H-USY-D samples shows a decrease in bulk molar Si/Al ratio of the same order of magnitude (2%), which can be extrapolated to all NH 4 OH treated samples (Table 2 ). These results are in line with the high and relatively invariable material yields (90-94 wt%; Table 2 ) obtained for all treatment times, leading to high "desilication effi ciencies" amounting to a maximal value of 30 m 2 g −1 % −1 for H-USY-C. [ 21,54 ] Note that the pH of the 0.02 M NH 4 OH solution is 10.8, close to the dissolution boundary of silica in water at room temperature. [ 55 ] Therefore, it can be postulated that upon contacting the USY zeolite with the NH 4 OH solution, similar to a classic base leaching method, Si is extracted from the zeolite framework by OH − mediated hydrolysis, resulting in larger pores.…”

Section: Densifi Cation Versus Leaching Strategiessupporting

confidence: 80%

Catalyst Design by NH₄OH Treatment of USY Zeolite

Aelst

Verboekend

Philippaerts

et al. 2015

Adv Funct Materials

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Hierarchical zeolites are a class of superior catalysts which couples the intrinsic zeolitic properties to enhanced accessibility and intracrystalline mass transport to and from the active sites. The design of hierarchical USY (Ultra‐Stable Y) catalysts is achieved using a sustainable postsynthetic room temperature treatment with mildly alkaline NH4OH (0.02 m) solutions. Starting from a commercial dealuminated USY zeolite (Si/Al = 47), a hierarchical material is obtained by selective and tuneable creation of interconnected and accessible small mesopores (2–6 nm). In addition, the treatment immediately yields the NH4+ form without the need for additional ion exchange. After NH4OH modification, the crystal morphology is retained, whereas the microporosity and relative crystallinity are decreased. The gradual formation of dense amorphous phases throughout the crystal without significant framework atom leaching rationalizes the very high material yields (>90%). The superior catalytic performance of the developed hierarchical zeolites is demonstrated in the acid‐catalyzed isomerization of α‐pinene and the metal‐catalyzed conjugation of safflower oil. Significant improvements in activity and selectivity are attained, as well as a lowered susceptibility to deactivation. The catalytic performance is intimately related to the introduced mesopores, hence enhanced mass transport capacity, and the retained intrinsic zeolitic properties.

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Section: Densifi Cation Versus Leaching Strategiessupporting

confidence: 80%

Catalyst Design by NH₄OH Treatment of USY Zeolite

Aelst

Verboekend

Philippaerts

et al. 2015

Adv Funct Materials

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“…At this point it is important to note that with the adequate combination of post-synthesis basic and acid treatments proposed in this work, it is possible to obtain mesoporous Theta-1 zeolites, with mesopore volumes up to 0.200 cm 3 /g, in the range of those reported in the literature for samples obtained under similar desilication conditions [25,30], but preserving more than 90% of their micropore volume. This was achieved by directly treating the alkaline treated zeolite in its Na-form with an acid solution, either HCl or oxalic acid, which in a single step will remove the alkali cation and the amorphous extra-framework debris formed during the desilication.…”

Section: Catalyst Characterizationmentioning

confidence: 59%

“…The desilication of TON zeolites to hierarchical micro-mesoporous structures has been addressed in two recent papers [25,30], but the results were not completely satisfactory.…”

Section: Methodsmentioning

confidence: 99%

“…Verboekend et al [30] described low desilication efficiency for ZSM-22 and severe pore blocking due to the presence of extraframework debris. Although mild HCl treatments were able to restore most of the micropore volume as compared to that of the parent zeolite, less than 40% of the initial Brønsted acid site density was restored.…”

Section: Methodsmentioning

confidence: 99%

“…The spectra plotted in figure 3-a shows that all acid bridging hydroxyls are still accessible to the probe in the calcined HT1-50, so the acidity decrease is not due to partial blocking of the pores, The use of acid treatment with 0.1M HCl has been described as a route for successfully restoring the microporosity of alkaline treated ZSM-22 [30], since by means of this treatment amorphous extra-framework Al species are washed away. These species were described to be mainly located on the external surface of the crystals, blocking the uni-directional channels of the TON zeolite.…”

Section: Catalyst Characterizationmentioning

confidence: 99%

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Improved THETA-1 for Light Olefins Oligomerization to Diesel: Influence of Textural and Acidic Properties

Martı́nez

Doskocil²,

Corma

2013

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Martínez, C.; Corma Canós, A. (2014). Improved THETA-1 for light olefins oligomerization to diesel: Influence of textural and acidic properties. Topics in Catalysis. 57(6-9):668-682. doi:10.1007/s1124. Abstract.The increase in diesel demand, especially in Europe, and the need for high fuel quality requirements, is forcing refiners to move into additional processes for production of high cetane diesel in order to meet the present market trends. Oligomerization of light olefins into middle distillate range products is a viable option. The fuel produced through this technology is environmentally friendly, free of sulfur and aromatics, and the adequate choice of the heterogeneous catalyst will direct the selectivity towards low branched oligomers, which will result in a high quality product. In this work we show the benefits of combining basic desilication treatments for generation of additional mesoporosity in mono-directional Theta-1 zeolite, with selective acid dealumination steps that restore not only the microporosity to values close to those of the parent samples, but also the total and strong Brønsted acidity. These modified Theta-1 zeolites present an outstanding catalytic behavior for oligomerization of propene, with a largely increased initial activity, a much higher resistance to deactivation with time on stream, and an improved selectivity to products in the diesel fraction, as compared to the original microporous Theta-1.

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